GH26139, DOC: Explicit statement of default complevel for HDFStore

Author: swyoon

pandas/io/pytables.py

@@ -423,6 +423,7 @@ class HDFStore(StringMixin):
     complevel : int, 0-9, default None
             Specifies a compression level for data.
             A value of 0 disables compression.
+            None is translated to 0.
     complib : {'zlib', 'lzo', 'bzip2', 'blosc'}, default 'zlib'
             Specifies the compression library to be used.
             As of v0.20.2 these additional compressors for Blosc are supported